This invention concerns a wood harvesting method used in forest work, defined in the introductory part of the patent claim. It also concerns the harvester head used for the implementation of this method which is described in the introductory part of the first patent claim for the device.
The typical Nordic wood harvesting chain utilises efficient methods that are mainly useful and most economical when harvesting timber trees. These methods make use of big multipurpose machines as the basic machines. These machines are indeed very efficient in processing single timber trees.
However, wood harvesting is not just harvesting timber trees. The harvesting of props, for example, is not nearly as cost-effective as timber harvesting when these traditional methods and machines are used, because the price received for props is lower, and the volume per tree is smaller.
In the conventional work with a multipurpose machine, not enough attention has been paid to the harvesting of fuel wood. Fuel wood is often actually rolled into the soil with a machine As regards cost-effectiveness, this is quite understandable, but it still leads to economical waste. In the same way, the first thinning is often completely neglected when using today""s methods and equipment, because it brings no momentary profit.
Some investments have been made in order to develop harvesting methods and equipment for fuel wood alone, but these are economically not very competitive, due to various reasons. Besides, they are unable to handle logs and possibly props as well.
The invention is targeted at bringing up a wood harvesting method and a harvester head capable of eliminating some bad sides of the above-mentioned harvesting methods. In particular, the aim is to introduce a method and a harvester head which make it possible to harvest props or fuel wood in bunches, so that the lack of efficiency due to the small size of a single tree is no more an issue. In addition, our goal is to introduce a harvester head that can also be used for harvesting timber trees one at a time.
The objective of the invention can be reached by utilising the method and the harvester head, which are characterised by the features presented in the parts of the patent claims describing the characteristic features of the invention.
When using the method suggested in the invention, the harvesting in bunches includes at least the following work phases essentially in this order: place the harvester head against the first tree with all the grapples open, close all the grapples around the first tree, cut the tree with the cutting device, lift the cut tree a little by holding it with the grapples fastened to a telescopic boom and using the stroke cylinder to move the telescopic boom in relation to the main body of the machine Holding the tree in an upright position, move to the next tree to be cut, place the harvester head close to the second tree, open the rigid grapples while holding the first tree up with the articulated grapples, and close the rigid grapples around the second tree The articulated grapples are thus left between the first and the second tree. Now open the articulated grapples, so that their turning tips are essentially forceless and can therefore easily slip away from between the trees, close the articulated grapples around all the trees and cut the second tree with the cutting device. Lift the cut trees a little by holding them with the grapples fastened to the telescopic boom and by using the stroke cylinder to move the telescopic boom in relation to the main body of the machine. After this, continue working in the above-described order, cutting and collecting more trees, until the grapples are full. In the end, the full grapple of wood is processed further according to current needs and/or loaded to an intermediate depot, on a transporting vehicle or to a device for further processing This method is very useful, in order to harvest the trees in bunches effectively and reliably.
The above-described method makes it possible to fell all trees to be used from a forest holding during a single visit of a harvester, regardless of the sizes of the trees when the versatile and effective harvesting equipment, as described in the invention, is available.
When applying the invention cost-efficiently, the branches of the trees are delimbed or bent from the outside with the grapples equipped with cutting blades by using the stroke cylinder to move the telescopic boom in relation to the main body of the machine and holding the trees with the other grapples. Thus, the bunch of trees requires less space and is therefore easier to transport.